Treating of motor fuels



Patented Mar. 1, 1938 TREATING or MOTOR FUELS Franz Rudolf Moser, Amsterdam, Netherlands, assignor to Shell Development Company, San Francisco, Calif.', a corporation of Delaware No Drawing. Application August 6, 1935, Serial No. 34,911, in the Netherlands September 21,

1 Claim.

This invention relates to a process for improving the knock rating of motor gasolines.

Certain gasolines produced by distillation from crude petroleum oils, shale oils and/or hydrogenated oils possess low octane number. Octane number is a unit for measuring antiknock value and is defined in method D-35'7-34T ofthe American Society for Testing Materials. It is-known that straight chain paraflinic as well as certain cyclic hydrocarbons are chiefly responsible for poor anti-knock properties of gasolines, and that byexposing gasolines containing badly detonating hydrocarbons to temperatures normally of the Order of 600 C. to 800 C. for a predetermined length of time, a change in the structure of some of the components takes place, which results in an improvement of the octane number of said gasoline. This process is called reforming. Reforming, however, has the disadvantage of producinga comparatively high percentage of fixed gas, which is usually of the order of about 25% or higher. Superatmospheric pressure may reduce the formation of normally non-condensible gases, but frequently not to an extent to warrant the construction of high pressure reforming units capable of withstanding the high'temperatures of reforming.

I have discovered that gasolines of low octane number, particularly straight run gasolines, can successfully be converted to gasolines of higher octane number without appreciable gas loss, if the vapors of the low octane number gasoline are conducted over suitable catalysts at moderate temperatures ranging from about 300 C. to about 525 C. The catalysts which I have found to be most efiective are inorganic phosphates and certain silicates. phates is somewhat dependent on the metal radical, the phosphates of metals of the first, second and third groups of the periodic system being most effective, although all inorganic phosphates which are stable at the temperatures of my process are capable of improving the knock rating of low octane number gasolines to some extent. Of the silicates, those which exhibit a large surface and which are not subject to sintering or decomposition with resulting decrease of surface are suitable. In particular asbestos and base exchanging silicates of the type of permutite are very effective. v

In practice, hydrocarbon vapors which may contain normal paraiflnic hydrocarbons of the type of gasoline and preferably produced by evaporation under substantially non-cracking conditions from a suitable mineral oil, are brought to The catalytic activity of the phos-' the effective conversion temperature and are conducted over the catalyst at a temperature which lies between about 300 C. and 525 C. The catain my process is much larger for a given gas loss than is the case in ordinary reforming. As in cracking, in my process the rate of octane improvement and gas formation increases with increasing temperature, but contrary to cracking in which over a wide temperature range octane improvement and gas formation follow approximately parallel lines, I find that within anoptimum temperature range of comparatively narrow limits of the order of about 25 C., a considerable octane improvement can be produced with practically no gas loss. The actual optimum operating temperature depends upon the catalyst and the material being treated and can be ready determined by experiment. The time of reaction must be carefully controlled because of its effects on the relation of gas formation to octane improvement under temperature and pressure conditions. The time should be so limited as to result in as high an octane number improvement as economical considerations with respect to gas losses will permit.

The improvement in octane number which can be achieved by my process usually ranges from about 5 to points, a 10 point raise being considered a fair improvement. Gas losses are usually of the order of 10% or less, and can consistently be held below 15%. It has been found that substantial improvements can be obtainedprinciv pally on relatively low octane number gasoline;

although superatmospheric pressures can be applied up to the point of incipient liquefaction of the treating stock at the temperatures of the number has a tendency further to reduce gas losses.

Catalysts which operate at a relatively low temperature generally permit an improvement in octane number accompanied by a smaller loss of gas than-is the case with catalyst requiring higher temperatures. This does not mean however, that a catalyst requiring an operating temperature of say, 500 C. will always produce a loweroctane gasoline than a 400 C. catalyst, since the opposite may often be the case; the gas loss .at the higher temperatures is usually found to be higher for equal octane improvement.

It is important that the catalyst be properly prepared to allow for maximum contact with the vapors passing over it. It should be granular, as in the case of permutite, or fibrous, as in the case of asbestos. If granular, it should preferably have a mesh size of 10 to 90 U. S. standard. Solid catalysts such as most phosphates may be prepared by simply disintegrating them and screening to the proper size, or by grinding and briquetting. Ground tertiary calcium phosphate, for example, was wetted with water. pressed into briquets and dried. The briquetswere broken into sections of about 10 mesh.

The catalyst may also.be deposited from solutions on a suitable carrier which itself may be inert or active. For instance, asbestos was wetted with a strong solution of. sodium phosphate, and was dried at about 200 C.

The prepared catalyst is placed into any suitable tower or container to form a filter-like bed through which the vapors are conducted.

The catalyst can be used for many hours before f it loses part or all otits conversion efllzciency.

Loss of efliciency is due to coke being gradually deposited on the catalyst, coke formation being the results of polymerization of olefines contained in the vapors. When the eflici ency of the catalyst has droppedto a point 01' insuflicient conversion, the reaction may be stopped or the hydrocarbon vapors may be diverted through another bed of catalytic material. Hot air is then passed over the spent catalyst to eflect combustion of the carbonaceous deposits. The temperature\ nd the, amount of air are preferably so contro ed to prevent the temperature in the bed oi catalyst to rise above about 800 C. during the process of; regeneration. At temperatures.

above 800 C. there is danger of permanently destroying the activity or some of the catalysts. In the following illustrative examples the type of improvement which my process is capable of imparting to low octane number gasolines is clearly shown.

Example I Fammpie II A. Mexican straight run gasoline having an octane number of 56 was conducted in the vapor state at a temperature of 500 C. over tertiary calcium phosphate. The octane number rose to 66.5 while the gas loss was, 12%;

Exampie III Vapors from a straight run 428s having an octane number oi 54 were conducted through a bed of permutite at 475 C. The octane number of the resulting gasoline was 61.5 and gas losses were below 10%.

Example IV A Mexican straight run gasoline with an octane number of 52 was conducted in vapor form at a temperature of 500 C. over asbestos of short fibre. The octane number was increased to 66.5 at a gas loss of about 12%.

I claim as my invention:

In the process 01' improving the antiknock rating of a gasoline distillate containing normal paraflinic hydrocarbons of a low antiknock rating, the steps comprising contacting the distillate in the vapor state with boron phosphate at a conversion temperature below normal reforming temperature for a time sufllcient to eflect a substantial increase in octane number but insufflcient to cause a gas loss or a magnitude characteristic of reforming.

FRANZ RUDOLF MOSER. 

